Plastic pipe cutters as used for shaving, milling and cutting the leading end of pipes are well known. Cutters for removing the hub of a pipe coupling have also been described in the literature. Such devices are useful in repair and replacement situations where a plastic pipe must be conditioned to receive a new fitting. They are most useful in situations where access to the pipe is limited, e.g., the pipe is embedded in and projects from a wall in such a way that replacement or extension of the pipe is not readily accomplished.
U.S. Pat. No. 4,691,600 to Carlson discloses a pipe shaving tool with recessed disk cutters mounted on forwardly projecting lugs positioned about an elongated mandrel. The Carlson device is mountable on a power drill or the like, and used exclusively for shaving the outer surface of a pipe to both a predetermined depth and length. The Carlson device has limited application, first because the cutters are recessed and secondly because the cutter position is not adjustable. Therefore, if the pipe or hub is too large to fit between the radiused gap defined by the lugs and the mandrel, the cutters can not access the hub. Furthermore, the Carlson device is not able to shave or cut a planar flange member or mounting fixture which is attached to the pipe. It is first necessary to cut the mounting fixture off the pipe end, for example, with a saw. Accordingly, the Carlson tool has limited applicability.
Another example of a pipe planing device is found in U.S. Pat. No. 4,693,643 to Heyworth. Heyworth describes a device for progressive planing of the interior of a plastic pipe which features a cylindrical pilot member, a shaft, and a rotatable hub. The rotatable hub includes circumferentially spaced and radially projecting spider arms on the end of which square cutters are recessed and fixedly secured. The cutters are fixed at a negative rake angle and their outer edges extend radially outward beyond the hub. The outer cutter edges are positioned on a radius to be flush with the inner diameter of a pipe. As in the case of other prior art reaming devices, Heyworth requires that the pipe be cut transversely before planing. Furthermore, the Heyworth tool is unable to remove members from the outside of a pipe.
Bowen, in U.S. Pat. No. 4,930,948, describes a specialized tool for valve seat refitting, the purpose being to simultaneously cut the three faces of a valve seat. To achieve this purpose, Bowen uses a rotary driven, cylindrical body portion with longitudinal, tangential slots to support adjustably mounted, variably positioned cutting blades. The blades project forwardly of the body in different orientations and at different lengths to cut all three faces of the valve seat for refitting.
The known devices possess general utility to remove hubs, sawed-off pipe joints, and the like, or specialized utility, e.g., to refit a valve seat. However, the known devices do not address or solve the problem associated with removal of mounted flanged pipe couplings or removal of fixtures having a diameter substantially greater than the diameter of the pipe. The prior art discloses pipe shaving devices for general use which require the cutters either to travel in a circular path moving inwardly from the outer diameter to the inner diameter of the pipe or to abut an pilot/guide during the cutting/reaming operation to maintain the cutters in a proper position.
Furthermore, during cutting operations with the prior art devices, the plastic shavings can accumulate in front of the device or cutter edges, resulting in non-uniform cutting. Some devices, such as those identified above, incorporate the cutters on projecting arms or spiders so that during the cutting operation the pipe shavings do not compress in front of the cutters but move into the gaps between the arms and may fall away from the device by gravity if the device is used in an open area. This method of temporarily removing the shavings from the cutter edges can lead to guidance and alignment problems when the shavings are allowed to accumulate and compact in front of the tool during use.